Results 1 to 3 of 3

Math Help - Area of shaded region. Limits in question.

  1. #1
    Junior Member
    Joined
    Jan 2011
    Posts
    35

    Area of shaded region. Limits in question.

    I'm having an issue with a particular question in that the limits are not being used (only the upper limit is being used). If I use only the upper limit, I get the correct answer, but if I use both limits, the area comes in -ve and becomes wrong.

    I would just like to know why.

    The equation of the following curve is: x^3-3x^2-9x+27.
    The integrated equation becomes: x^4/4 - x^3 -9x^2/2 +27x.

    Here's the figure:



    Using x=3 gives us 33.75 as the area. This is the answer.
    But what about x=0? If I use this and subtract the results, I get -47.25.

    Any explanation would be helpful.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,697
    Thanks
    1512
    What do you get if the function x^4/4 - x^3/3 - 9x^2/2 + 27x is evaluated at x = 0? What happens when you subtract this answer from 33.75?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jan 2011
    Posts
    35
    Thanks for the reply.

    I just found and realized the mistake I was making after looking at your post. I was constantly taking, even for the x=0 limit, the x=3 limit at the 27x portion. So, instead of taking x=0 at 27x which would become 27(0) or 0, I was taking x=3 which would become 27(3) or 81, and subtracting that from the x=3 evaluation. It's going to be simply 33.75 - 0.

    Well, like I've said earlier, I'm not good at mathematics and I tend to make these simple mistakes frequently without even realizing it.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Area of shaded region
    Posted in the Algebra Forum
    Replies: 1
    Last Post: August 11th 2011, 10:36 PM
  2. Find the area of the shaded region...
    Posted in the Geometry Forum
    Replies: 2
    Last Post: February 25th 2010, 09:01 AM
  3. calculate area of shaded region
    Posted in the Calculus Forum
    Replies: 6
    Last Post: April 30th 2009, 10:38 AM
  4. Area and limit of the shaded region...?
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: September 16th 2008, 02:18 PM
  5. Area of shaded region
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 7th 2008, 07:02 PM

Search Tags


/mathhelpforum @mathhelpforum